Muscle car plus motor head does not equal muscle head, although it could. The first pair evokes positive images for those who remember Holley carburetors, dual exhausts, Hurst shifters and four on the floor (gears, that is). The muscle cars of the 60’s were exciting to drive and fun to work on. That was an era when there was enough room in the engine compartment to swing a socket wrench. Of course, without air conditioning there was plenty of space to climb inside and yank a Champion or two. Considering that engine oil is to a car what blood is to the human body, you can bet that oil changes were dutifully timed events. Unlike blood, oil has changed over the years. Modern engine oils have viscosity-index improvers, antioxidants, dispersants, corrosion and foam inhibitors, and anti-wear agents that were absent half a century ago. Also some oil formulations vary from state to state. In the past, wearing oil and grease on hands and clothes was a badge of honor, an announcement that proclaimed mastery over a demanding technology. Today, protective gloves need to be the order of the day.

Mechanics and other auto workers who are exposed to used crankcase oil have experienced skin rashes, blood effects similar to anemia, headaches and tremors. Along with used oil, they are exposed to other chemicals/toxins common to the auto industry, including fluids, metal particles and fumes. Used oil may contain chemical constituents that result from the internal combustion process, such as the polycyclic aromatic hydrocarbons (PAH) associated with benzene and related suspect carcinogenic compounds. Systemic effects of exposure to used oils and automotive fluids may include elevated blood pressure, aberrant red blood cell values (caused by lead exposure), stress to the liver (as indicated by irregularities in enzyme markers), and skin rashes (Clausen and Rastogi, 1977). In mechanics who work with new cars, interior cabin materials present no less a threat to health. Exposures to high concentrations of the aliphatic hydrocarbons that render the appealing “new car smell” are found to accumulate in the body (Yoshida, Jan 2010 and Aug 2010).

What’s the big deal?

There is more than one route to internal toxicity. You can swallow almost anything, inhale too many other things, and absorb more than a handful of the remaining damaging substances available to the environment. Compounds that contain only hydrogen and carbon are called hydrocarbons. The number of atoms of either element can change to make a different substance, one of the simplest being CH4, known as methane. During the refining of petroleum, one kind of hydrocarbon can be converted to another, giving us gasoline, naphtha, kerosene, lubricating oils and more. Adding chlorine to the C-H backbone reduces flammability and increases stability, resulting in chlorinated hydrocarbon solvents that can be used to clean, degrease and thin almost anything. At high temperatures that vary according to the compound, they give off seriously toxic gases and can enter the body through the skin.

Most foreign substances are unable to penetrate skin, the outer layer of which is an effective barrier to most inorganic particles. But damage to the stratum corneum, whether by abrasion, exposure to U-V light, or by chemical insult, can allow penetration. Lubricating oils, some waxes, and greases can induce primary irritations and photosensitivity to skin. The severity depends on the nature of the oil, the integrity of the skin, the frequency and length of contact, and individual susceptibility. Certain size molecules of chlorinated and simpler hydrocarbons, and of those with a greater number of carbon atoms than hydrogens, are more apt to enter skin than others (Riihimaki and Pfaffli, 1978) (Babu et al, 2004).

Among the riskier materials are automotive and industrial solvents made with trichloroethylene or tetrachloroethylene, known to penetrate the skin and suspected of being carcinogenic. Up to the 1970’s, trichloroethylene was used directly on humans as a general anesthetic and as a wound disinfectant. Believe it or not, it was also used as a flavoring agent for coffee. This nonsense was halted in 1977. Today it’s being used as a degreaser, as a cleaner for textiles, as an additive to inks and paints, and as an ingredient in PVC (the polyvinyl chloride in plastic plumbing). At least it won’t catch fire. Strangely, the metabolites of trichloroethylene are identical to those that follow the chlorination of municipal water supplies, namely chloral, chloral hydrate, monochloroacetic acid, and di- and trichloroacetic acids (Simon, 2005).

Tetrachloroethylene is also known as perchloroethylene, most commonly used in dry cleaning. Exposure, either respiratory or dermal, may cause depression of the CNS, liver and kidney damage, impaired memory and headaches (DHHS, 1991). Like trichloroethylene, it is non-flammable and stable. Earlier in its history it was used in commercial refrigerants and auto air conditioners. But it’s an excellent solvent for organic materials such as the greases and lubricants used in the automotive industry…and it dissolves fats from skin, resulting in skin irritation.

Does It Hurt?

Once in the body, either through the skin or the nose, these hydrocarbons attack the cell membrane and the proteins that prevent entry of toxic compounds. A bodyguard enzyme called ATP-ase directs cell traffic by letting food and energy in, and by escorting wastes and toxins to the door. Another of its jobs is to control the balance of sodium and potassium. Sodium tells a cell to contract so you can pick up a tool, and potassium tells it to relax so you can put it down again. Chlorinated solvents, though, attack the fats from which the membrane is made and cause it to lose its shape and to resemble a half deflated basketball. Now, it can’t do its job and you get tired quickly and your thinking becomes foggy. Once ATP-ase gets dissolved by chlorinated hydrocarbons, any work that requires muscle power becomes more and more difficult. There are no alternatives to crankcase oil, but there are optional solvents and degreasers. Read the labels, wear gloves, and protect your eyes. No matter how thick-skinned we think we are, we really aren’t.